Due to aging, joints of human beings may suffer wear or degradation caused by long term use or degeneration, leading to pain or incapability of providing proper moving functions, as a consequence of which daily living is affected. When a joint suffers severe pathological changes, artificial knee joint replacement provides a measure to release the pain and improve joint function. The artificial knee joint is often composed of components made of metal or plastics and can be fixed to bones to replace the original knee joint to restore the normal function of the knee joint.
Total knee arthroplasy (TKR) is a common surgical procedure to treat degradation or lesion of knee joint. A typical artificial knee joint comprises a femoral component, a tibial baseplate, a tibial insert, and a patellar component. The tibial baseplate is fixed to a tibial surface, and the tibial insert is coupled to the tibial baseplate through mechanical locking mechanism. The stability of the knee joint heavily depends on the constrained design between femoral component and tibial insert which was locked with tibial baseplate. Therefore, how to secure locking strength between the tibial insert and the tibial baseplate was one of most important issue to achieve successful TKR. The tibial insert forms thereon a support that constrains the movement between the femoral implant and the tibial insert, but it is often made of plastics and is susceptible to fracture caused by long resistance against external forces acting thereon. Daily activity of human beings causes loads and shear forces acting on the artificial knee joint, especially the tibial insert post and this may cause dislocation between the tibial insert and the tibial baseplate, or may even separate the tibial insert from the tibial baseplate. Thus, the support formed on the tibial insert must be of sufficient mechanical strength and proper coupling between the tibial insert and the tibial baseplate is important and necessary.
An L-shaped reinforcement inset in the tibial insert is a common way to improve the mechanical strength of the support formed on the tibial insert. Since a metal object is inset in the support of the tibial insert, the mechanical strength of the support for resistance against external forces is increased. However, this arrangement only improves the stability between the tibial insert and the femural implant. One common way for coupling the tibial insert and the tibial baseplate is using a bolt to joint the two components. This only improves the coupling between the two components, but does not increase the capability of resisting shear force. Further, the bolt and the tibial insert are separate parts, which are combined together only when they are put into use. This lowers the efficiency of operation.
Thus, a good design of artificial knee joint must offer: (1) sufficient stability for movement of the knee joint for reducing unnecessary activity or dislocation of joint, (2) sufficient strength for resisting external forces, (3) protection against excessive wear of implants for extension of lifespan of the implants, and (4) improved operation efficiency for reducing the time required for surgical operations.
In view of the above drawbacks, the present invention aims to provide a novel design of orthopaedic implant that overcomes the above problems.